Glacier meets sea in Diksonfjord, Greenland.
Jane Ricks/Alami
The Arctic will continue to warm by about 1.5°C even if atmospheric carbon dioxide levels return to pre-industrial levels and the planet as a whole cools.
The region is also forecast to continue to experience around 0.1 millimeters per day of excess rainfall, regardless of whether we deploy large-scale carbon dioxide removal (CDR) projects.
“These results highlight the irreversible nature of climate change in the Arctic even under aggressive CDR scenarios,” the researchers wrote in the study.
Atmospheric CO2 levels are currently about 1.5 times higher than pre-industrial levels, and the Arctic warm more than 3°C. A study Data published in March showed that average sea ice extent would remain 1 million square kilometers less even if excess CO2 was removed.
In a new study Xiao Dong from the Institute of Atmospheric Physics in Beijing and colleagues predicted the Arctic's potential for continued warming using 11 independent climate models. First, it assumes precipitation will also remain elevated, he says. Michael Meredith from the British Antarctic Survey, who was not involved in the study.
The main reason is that the ocean, which has absorbed 90 percent of the heat from global warming, will continue to warm the Arctic for centuries even as the atmosphere cools. This can be exacerbated by feedback loops such as the loss of sea ice, allowing open water to warm the air.
“Even if you cool the atmosphere, the ocean will lag behind and resist it,” Meredith says.
Because of the financial and energy costs involved, many are skeptical that CDR, which involves planting trees and sucking CO2 out of the air using fans and chemical filters, will be able to significantly reduce CO2 emissions into the atmosphere – a process that would otherwise take thousands of years.
Dong and his colleagues analyzed an abstract scenario in which atmospheric CO2 levels increase four times above pre-industrial levels over 140 years, decline over 140 years, and remain at pre-industrial levels for another 60 years.
They also analyzed a potential real-world climate scenario in which humanity cuts emissions immediately, as well as a scenario in which we continue to have high emissions but then rapidly increase the CDR starting in 2070. In these two scenarios, they found that the Arctic would warm by about 1.5°C and would continue to receive an additional 0.1 millimeter of precipitation per day in 2100, the same as in the abstract scenario.
Models predict that, unlike the rest of the far north, temperatures and rainfall will decline in the stretch of ocean south of Greenland and Iceland. This suggests that the Atlantic Meridional Overturning Circulation (AMOC) will transport cooler surface waters from the tropics into the area. Research suggests that this current, caused by differences in the temperature and density of ocean waters, is already slowing as the global ocean warms, a trend that could eventually lead to much colder winters in Europe.
Climate effects such as thawing permafrost and the melting of the Greenland ice sheet are also likely to continue, although the study did not model them.
“You would expect the Greenland ice sheet to behave as we see it, which is to continue to lose mass and contribute to sea level rise,” says Mark Serreze at the US National Snow and Ice Data Center.
While this study suggests the Arctic will remain warmer for several centuries, it should eventually cool over many additional centuries or millennia, he adds.
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